If anyone has made a 'lifestyle' choice to remain in their own property but be accommodated at a unit then they should pay the same as the singlie.
I'm not an HQ Air 'beanstealer' but would argue that married individuals elect to live in messes during the week because the accommodation is free. Start charging those individuals the same cost as singlies and you will see a huge increase in the demand for married quarters, which in some areas would probably cost less to rent than living in a mess. Places like HWY and NWD would break very quickly and the cost to MOD would be astronomical renting all those 4 bedroom detached houses in North West London and Princes Risborough!